Identify from the following species in which d² sp³ hybridization is shown by central atom :

Solution

Chemistry ma’am · 3 steps

Check where the d orbitals come from: d²sp³ uses the inner (n−1)d shell, sp³d² uses the outer nd shell.

1. Order of orbitals. Both d²sp³ and sp³d² mix six orbitals and give an octahedron. The order tells you which shell supplies the d orbitals. In d²sp³ they are the inner (n-1)d orbitals, which only a transition metal ion can offer empty.
2. Cobalt complex. Co³⁺ is 3d⁶. NH₃ is a strong field ligand for Co³⁺, so the six electrons pair up in three 3d orbitals and two 3d orbitals stay empty. Those two 3d orbitals mix with 4s and 4p to give d²sp³, a low-spin inner orbital complex.

   Species	Central atom	Hybridisation	d orbitals used
   [Co(NH₃)₆]³⁺	Co³⁺, 3d⁶, 6 ligands	d²sp³	inner 3d
   SF₆	S, 6 bond pairs	sp³d²	outer 3d (n = 3)
   [PtCl₄]²⁻	Pt²⁺, 5d⁸, 4 ligands	dsp², square planar	one inner 5d
   BrF₅	Br, 5 bond pairs + 1 lone pair	sp³d²	outer 4d (n = 4)

3. So. Only [Co(NH₃)₆]³⁺ uses inner d orbitals with six bonding pairs, so the answer is (a).

The idea to keep. Same octahedron, different label: d before sp means inner (n−1)d orbitals from a transition metal ion, d after sp means outer nd orbitals, as in a main-group atom.

Answer from the NTA final answer key. Solution by PrepWiser.